Semiconductor chip manufacturing does not typically enjoy the high level of automation that other technology sectors do. In various areas of a semiconductor chip manufacturing factory, the systems and tools are often only semi-integrated or even completely independent. Furthermore, because of the proprietary communication protocols that are typically used, it is often very difficult to automate the manufacturing process in a way that not only coordinates the activity between the tools, but also collects data from the tools in a fashion that is usable for process improvements and other job management functions.
FIG. 1 illustrates a prior art approach to equipment management. Factory manufacturing execution system (MES) 110 is connected to semiconductor manufacturing equipment 120, running Tool Control Software 130. This traditional approach to managing equipment via computer integrated manufacturing technologies relies on the twenty-year-old Semiconductor Equipment Communication Standard (SECS) communication standards of the Semiconductor Equipment and Materials International (SEMI) organization. These standards define a serial point-to-point communication interface and a messaging system for the exchange of information between semiconductor manufacturing equipment 120 and MES 110. To comply with these standards, tool vendors typically supply SECS or SECS/GEM-compliant interface 140 and Tool Control Software 130 to enable factory personnel to connect the tool to MES host 110.
As tools have become increasingly complex, there has been a need for more information about the capabilities and structure of the tools than the SECS messaging system and interface typically provides. Some of the specific limitations of the SECS interface include the following.
1. Undiscoverable interfaces: the MES cannot query the interface to determine its capabilities. Tool drivers have been developed to supply the MES with configuration information not available through the SECS interface.
2. Undiscoverable physical structures: SECS messages do not reveal the physical structure of a tool. This prevents the development of generic factory systems for important tasks such as remote status display and remote diagnostics.
3. Single client: The SECS cable connecting the tool to the MES is a point-to-point link. Only one software process from the MES can access the tool, making it impossible for multiple client applications to access the tool.
4. Lack of a security mechanism: SECS has no provision for client authentication or access permissions. If multiple clients, especially those external to the MES, can access the tool, security control must be available.
As an alternative to the configuration illustrated in FIG. 1, factory automation engineers have developed configurations, exemplified by FIG. 2, in which tools are grouped together and loosely controlled by a monolithic software program known as a “station controller.” Station Controller 250 communicates with either an individual tool or a group of tools using the SECS/GEM interface. Factory MES 210 is connected to Station Controller 250, which is in turn connected to semiconductor manufacturing equipment 220, running Tool Control Software 230.
The job of Station Controller 250 is twofold. First, Station Controller 250 presents MES 210 with a more convenient view of the tool than possible using the SECS interface. Second, Station Controller 250 can add several capabilities to the tool, such as process job setup and recipe control.
Unfortunately, current software architectures implementing station controllers have severe restrictions, in particular with respect to integration among semiconductor manufacturing tools and the way that data about tool actions and status is handled. In particular, there is often a need for the equipment to provide real-time data directly from the tools to other software applications for the purpose of manufacturing process analysis, diagnosis, and quickly implemented corrective actions. To support this requirement, the current software architectures used to integrate and extract data from the tools has many design impediments to overcome. Primarily, current architectures implementing station controllers have not overcome the limitations stated above with the SECS/GEM interface.
Another fundamental problem present in current station controllers is higher complexity as a result from a drift from the primary function of controlling material processing. As multiple functions have been incorporated on top of core job management needs, large and complex software architectures have been created that are not easily adaptable to change. This also results in a single point of failure with multiple internal failure points and a high cost of ownership. Because data collection has typically been integrated with job management, current station controllers have become the sole collectors of equipment data, requiring data consumers to interface through the station controllers.
The changes in the semiconductor industry that have mandated that semiconductor manufactures implement efficient automation integration strategies is primarily attributed to the resulting exponential increase in manufacturing data that must be managed as circuit capacity increase with 300 mm wafers and beyond, in parallel with reductions in geometry size which are now focused on 45 nm and below. In addition to the above drivers for change, several other pressures are magnifying the need for change. First, a need exists to focus a small number of expert resources on solving issues, and to reduce the resources spent on merely finding data. Also, the high cost of mis-processing wafers at 45 nm, where each wafer consists of 100's to 1000's of die, has made the need for efficient solutions more acute. There are also performance issues that are driving the need for efficient solutions, such as the high cost of equipment downtime and the desire to improve overall equipment effectiveness (OEE). There is also a need for real-time data to allow faster response to processing issues and a need to improve the tool to production time.
Current solutions will not solve the data access requirements for applications such as e-Diagnostics and Advanced Process Control (APC) that require the ability for automation architectures to support concurrent multi-client access to equipment and independent of the current ownership of equipment processing control. The ability to implement “data on demand” is a driving factor in the next generation of semiconductor focused station controller architectures. As the industry moves from lot based to wafer level manufacturing, automation solutions will need to be able to provide advanced statistical process control (SPC), fault detection classification and run-to-run control applications required to make effective manufacturing and business decisions to meet the demands of their customers.
For the reasons stated above, the typical station controller has become an impediment. Where once the station controller was designed to specifically control management of manufacturing jobs, now the station controller has evolved into an intricately intertwined set of programs whose functions have expanded as much as its complexity. This complexity makes maintenance or changes to the station controller, as well as to its fundamental functions such as job management, very difficult, time consuming and expensive. In some cases the overlapping and intertwined nature of the software code makes factory managers very hesitant to make any changes, even if they would result in manufacturing process improvements that are required in order to increase the output yields of operating semiconductor chips.
New standards, such as SEMI E120, Specification for the Common Equipment Model (CEM) are evolving that provide standard equipment object models. CEM can be used as a guide to allow the development of object models that represent the external view of a tool to be used by other factory equipment. Standards such as CEM represent an opportunity to use an industry-standard object-oriented tool interface, but current station controller architectures are unable to take advantage of these new standards.
What is needed is a method to overcome the limitations of the SECS or SECS/GEM interfaces, eliminate the need for costly station controllers, and take advantage of the CEM object model.